A process for polymerizing a cyclic olefin by using a polymerization catalyst comprising a tungsten compound, a molybdenum compound, a ruthenium compound or an osmium compound has hitherto been well known. The polymer produced through ring-opening polymerization according to this process has poor heat-stability because of the presence of double bonds in the backbone chain. As an improvement of this process, a process for hydrogenating a polymer prepared through ring-opening polymerization has been proposed.
For example, a process has been proposed wherein a cyclic olefin is polymerized through metathesis ring-opening polymerization by using a transition metal compound having tungsten or molybdenum as a central atom, and then, a hydrogenation catalyst is added to hydrogenate carbon-carbon double bonds in the backbone chain of the polymer (Japanese Unexamined Patent Publication (hereinafter abbreviated to, “JP-A”) No. H5-271326, JP-A H9-77853 and JP-A H10-195183). However, when a hydrogenation catalyst is added into a polymerization system as prepared by using a tungsten or molybdenum-containing polymerization catalyst, to hydrogenate a polymer thus-prepared through ring-opening polymerization, the polymerization catalyst poisons the hydrogenation catalyst. Therefore, the hydrogenation reaction must be carried out after the polymerization catalyst is removed from the polymerization system, or a large amount of the hydrogenation catalyst must be used.
In JP-A H10-195182, a process has been reported wherein a cyclic olefin is polymerized through ring-opening polymerization using a catalyst comprising ruthenium-carbene compound, then a modifier such as ethyl vinyl ether is added to modify the catalyst, and then the as-produced polymer is hydrogenated in the presence of the modified catalyst. This process is advantageous in that the polymerization step and the hydrogenation step can be consecutively carried out. However, the present inventors have found that hydrogenation reaction does not-proceed often to the desired extent in this process. Further, the above-mentioned catalyst is a homogeneous catalyst and thus the separation and removal thereof from the polymerization system is troublesome.